java try catch finally return 继续

之前在博客中有一篇文章讨论过异常中return值的情况，有兴趣可以参见 http://gaofulai1988.iteye.com/admin/blogs/2259371，当时的例子比较简单，今天来了特殊点的例子。

在上例子之前，还是回顾以下之前的几个要点：

1. throw 后面的代码是不会执行的。
2. 不管是否有异常，都会执行finally。
3. 不管有多少个return, 只会执行finally里的return。

public static int doexception(){
		int x=0;
		try{
		  throw new Exception("aaa");
		}catch(Exception e){
			System.out.println("catch exception");
			return ++x;
		}finally{
			System.out.println("finally ....");
			 ++x;
		}
	}
	public static void main(String args[]){
		System.out.println("return value:"+doexception());
	}

此时的答案是多少呢？

catch exception
finally ....
return value:1

进入了finally里了，但是不是2， 是1?! 不可思议！看来只能找Oracle来帮我们解答了。

引用

If the try clause executes a return, the compiled code does the following:

Saves the return value (if any) in a local variable.

Executes a jsr to the code for the finally clause.

Upon return from the finally clause, returns the value saved in the local variable.

The compiler sets up a special exception handler, which catches any exception thrown by the try clause. If an exception is thrown in the try clause, this exception handler does the following:

Saves the exception in a local variable.

Executes a jsr to the finally clause.

Upon return from the finally clause, rethrows the exception.

http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.10.2.5

现在明白了吧，进入到finally里后的操作其实没有什么用，因为之前的变量已经被保存起来了。